1. Field of the Invention
The present invention relates to a mechanism for supporting movable members in an apparatus such as a lens barrel, and more specifically, relates to such a mechanism which includes a backlash eliminating structure.
2. Description of the Related Art
Play (backlash) is structurally indispensable between two members movably sliding on each other. However, since backlash concurrently has an influence on the accuracy of movement of the movable members, various types of backlash eliminating structures or mechanisms have been proposed. For instance, a lens barrel in which a rotating ring such as a cam ring for moving one or more lens groups in an optical axis direction continues to be extended forward from a lens barrel retracted position until reaching a ready-to-photograph position in a photographable range. However, the structure of a mechanism for eliminating backlash of such a rotating ring tends to be complicated.
The assignee of the present invention has proposed a solution to this problem in U.S. patent application Ser. No. 10/646,872. In this patent application, a first annular rotatable member and a second annular rotatable member which are supported to be movable relative to each other in an axial direction and integrally rotatable are provided inside an annular member, while a first sliding surface of the first annular rotatable member and a second sliding surface of the second annular rotatable member are biased to be in contact with a pair of circumferential surfaces formed on an inner peripheral surface of the annular member, respectively, to thereby make it possible to eliminate backlash by a simple backlash eliminating structure.